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The mortise and tenon joint is a staple of woodworking. Creating them can pose a few challenges. Building a custom jig with the size and orientation of the joints is fine if you only need a single size and shape. But if you find yourself making several jigs to cover the varied m&t joints in even a single project then a variable jig is something you should consider.

The Leigh Jigs Super FMT Mortise and Tenon jig is a very nice answer to this challenge. The joints are created by using an array of snap in guides that allow you to cut a large variation of tenons and corresponding mortises.

A specialized router base predrilled with many holes that allow it to receive many of today’s most popular routers. Aligning and attaching the base to your router is something that needs care and precision. In fact every step of aligning the jig is crucial. Any mistakes here will show up on every cut you make. Unfortunately with the selection of routers these days leigh can only write detailed instructions for some of the steps but is can be a bit vague when it comes to your specific router. It would be unrealistic to expect any more then that.

After getting the plate attached to the router and adjusting the collet to the perfect center using a centering mandrill, I was ready to make some sample cuts. Marking the location of the joint and adjusting the final alignment with a crosshair marker. Tightening the 2 F-clamps used for holding the wood firmly in place. The clamps are held fast to the jig with powerful magnets to keep them from falling onto the floor when you loosen them. This is a well thought-out feature, and one I found very useful.

Once you have the router plate mounted accurately you are ready to start cutting mortises. The operation is fairly simple. You begin by marking the centers of the mortise and the tenon, lining up the wood to the exact place you want the joint. Then you select the guide and bit that will produce the correct size of tenon. Snap the guide in place. Next you center the piece of wood that will have the tenon in it using the bulls eye attachment. Then you lift the router in place being careful to fit the pins into their proper location. Then it is as simple as removing the wood carefully as with any routing work. With the inclusion of the vacuum attachment (sold separately) the debris was cleared away fairly well keeping the work area pretty clean.

Next I aligned the board where the mortise was to be cut, again using the same cross hair guide, now adjusted correctly. Moving the plate pegs into the mortise guide the bit is limited to left and right movement only. Plunging carefully into the wood I cut the mortise with as much ease as the tenon. Removing the piece of wood from the jig I pressed the joint together. The alignment of the joint was off about a 32nd of an inch. I turned to the crosshair guide and realigned it by using a pair of adjustment screws as directed in the manual. Repeating the sample cut this time with perfect results. Over the next week I tried many of the size and shape guides, from very large tenons to tiny ones the Super FMT performed excellently.

With the current economy these days (or lack there of) it is unfortunately a large factor when buying tools for your woodshop. The Super FMT is priced at around $520 with the addition of the various accessory kits which range from $99 to $280 depending on the selection you want you can invest around $700. This is a substantial amount for a single use, dedicated machine. I hate to say it, but if you only find yourself needing a dozen or so m&t joints over the course of a year this is probably not an investment I would make. But if you need a larger amount of mortise and tenon joints then this is an excellent jig for you. The repeatable accuracy of the Super FMT and the quality of the workmanship by Leigh Jigs shows up in the finished product.

So, to sum up, Leigh has created an excellent jig, with repeatable accuracy. The price is a bit too high if you do not need to make a lot of m&t joints. But if you need enough of these joints then this is a tool you should consider.

Daniel

Available from Rockler

Leigh Super FMT Frame Mortise and Tenon JigEnjoy the same speed and precision of the FMT at a fraction of the cost! The same great features produce the same great joints. Simplicity is the key. The Super FMT uses just one bit, one guide and ..